Two weeks ago, Facebook announced App Links, a proposed standard for routing traffic between mobile applications. If the app developer community adopts the App Links standard, there will finally be a cross-platform standard for linking between apps. It will also help drive significant new revenue for Facebook’s ad products.

There has been a fair amount of confusion about what App Links means, so let’s clear the air first.

App Links is a proposal released by Facebook that shows app developers how to send users clicking links within their apps to the apps corresponding to the destinations in the links. This is hard to grasp, so let’s discuss an example use case from end to end:

An email mobile app like Mailbox can implement the App Links standard in its app itself, or by using an open-source library Facebook released called Bolts.

When a user opens the Mailbox app on his or her phone, the real process begins.

Mailbox then tries to send the user to deep links found in the App Links header tags on Hulu’s website for that user’s device.

If the user has the Hulu app installed, Mailbox sends him or her to the correct deep link.

If the user does not have the Hulu app installed, Mailbox sends him or her to the Hulu website.

Essentially, when a user clicks a link and the referrer app and the destination app both support the App Links standard, the user will be sent to the Hulu app if they have it installed, or to the website if they do not.

App Links Still In Early Days

There are a few important things to note. Both the referrer and destination apps must support the App Links standard in order for the user to be sent to the destination app. At launch, Facebook, Mailbox, and Spotify have implemented the standard in their apps, and 11 destination websites support the App Link tags. So today, when users click on links in Facebook, Mailbox, and Spotify for the 11 destination sites that support App Links, the user will be deep-linked if the user has the destination app on his or her smartphone.

While the App Links standard only works for specific use cases today, Facebook hopes to grow its adoption so that it will eventually work for all links on mobile. In order to make this standard ubiquitous, Facebook will need app developers to support it. Leveraging Parse’s developer-relations capabilities should enable the social network to accomplish this. However, it will also need major players like Google and Yahoo to support App Links in order to ensure that when any link is clicked in Gmail, Yahoo Mail, or popular apps, the App Links standard is leveraged. Getting Google, Yahoo, and other major players to support App Links could prove more challenging, however.

Another important note is that the App Links standard is a proposal for how to send users clicking on links in one app to a destination app. It does not discuss users clicking on mobile websites and sending them into destination apps. For example, if a user clicked on a Hulu link on the Facebook mobile website, the App Links proposal does not provide a description for linking into the Hulu app. This makes the proposal extremely useful for app-to-app linking, but less so for Web-to-app linking. In order to let marketers send one link that works for both app-to-app and Web-to-app linking, URX released omnilinks, a link that works everywhere today.

Why Does App-To-App Linking Matter To Facebook?

So, why is Facebook proposing a standard for how to link from app to app? There is a clear need for a single standard for how apps link to one another so developers can easily link to each other’s apps. By releasing open-source projects to make it easier for developers to link to other apps, Facebook is helping kick-start the movement. In addition, App Links will help advance Facebook’s ad business.

By having data from App Links tags and the Facebook App Links Hosting API in its App Links Index, Facebook will understand how Web links map to deep links in Android, iOS, and Windows Phone apps. The holy grail for ad platforms is allowing advertisers to create one campaign that works across desktop Web, mobile websites, and mobile apps. If the App Links standard takes hold, Facebook can do just this by leveraging its App Links Index. The advertiser would just input its Web link and an image into the Facebook Ad Editor for a re-engagement campaign, and it can work across desktop Web, mobile Web, and mobile apps. The advertiser just needs to add App Links tags to its site. If a user clicks the ad on Facebook on desktop, they will go to the advertiser website. If a user clicks from the Facebook mobile app, Facebook can check its App Links Index for App Links tags for that destination and route the user to the app page.

This means Facebook can begin heavily cross-selling their desktop advertiser customers to run re-engagement campaigns on mobile with no account changes. It wouldn’t be surprising if Facebook converted all Facebook ad campaigns to cross-platform campaigns for websites and apps in a similar way to what Google did for mobile Web and desktop Web with enhanced campaigns last year.

The App Links standard will also empower Facebook Audience Network, the social network’s third-party, in-app mobile ad network. When a publisher app serves ads, Facebook can read the App Links tags of the destination URL (or look at its App Links Index) to know what deep link to launch if the user has the associated app installed.

The ability for Facebook Audience Network to safely deep-link into destination apps will allow its inventory to quickly gain traction with mobile re-engagement marketers. Other mobile ad networks will eventually have a solution to the deep-linking problem, as well (in operating system, browser, or ad unit leveraging the App Link index), but likely not until deep-linking technologies solidify and gain serious adoption across app developers.

Enabling advertisers to start one campaign on Facebook ad inventory and Facebook Audience Network for desktop Web, mobile Web, and mobile apps simplifies advertising on Facebook and will lead to much higher utilization of all of its ad products.

When An App-Linking Standard Becomes Ubiquitous

When one standard begins to take hold in a majority of apps and websites, consumers will have a more seamless experience on mobile. When you are using an app or are on a website, you will click links that take you into the app to the page you want or to the website if you don’t have it installed. But, that is just the beginning. Once there is a standard for how to route traffic between apps, you will start seeing content from your favorite apps in other apps through strategic partnerships. Google announced that putting an Uber option in its Google Maps app so when you are looking for directions, you can press to open and book an Uber for your route. You can expect to see many more experiences like this pop up in mobile over the next few years.

With App Links, Facebook has put a stake in the ground in terms of how mobile apps could route traffic to one another. Other giants are sure to follow suit and may be able to implement app-to-app linking at the OS level. Ultimately, the winner will be able to provide better holistic advertising campaigns across mobile and desktop.

In part two of this series, we will discuss possible solutions Google and Apple could propose to enable app-to-app linking and how they compare to App Links.

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